Valve-operating mechanism



Mnrchi.' 1922!.V 1,529,201

- E. w. MEREDITH VALVE OPERATINGy MECHANI SM Filed Jan. 18, 1924 Patented Mar. 10, 1925.

UNirE-o STATES EDWARD W. MEREDITII, 0F PUNXSUTAWNEY, PENNSYLVANIA.

VALVE-,OPERATING .ivrn'ciinnrsivr Application filed January 18, 1924,. erlal No.

To au whom t may concern.'

lBe it known that I, EDWARD W. Munn- DITH, a citizen of the United States of America, residing at Punxsutawney, in the county `of Jefferson and State of Pennsylvania,have invented certain new and useful Improvements in Valve-'OperatingA Mecha-` nism, `of which the following is. a specification.

Mypresent invention relates to improvements in valve operating mechanism for internal combustion ,engines of the reeip'rolcating'typeeand particularly tothe means for actuating the exhaust valve thereof. i' lThe invention involves certain novel'features of construction and combinations and'arrangements of parts in the construction and'operation of the exhaust valve mechanism whereby the valve' which is normally held open under tension of a spring when the usual cam and'tappet device are inoperative, may be closed by motive Huid pressure at predetermined intervals. As herein illustrated the valve operating mechanism is utilized in a four cycle, eompound engine, wherein the combustion charge enters a single working cylinder, and after ignition at high pressure expansion .b'elowthe' piston head on the upstrolre of the pistonfthe burned gases of combustion, before being exhausted are transferred and utilizedatna lower pressure expansion on the 'top ofthe piston head for applying power to the succeeding down stroke of the reciprocating piston. After the second expansion the `gases of combustion are exhausted through the exhaust outlet with comparatively slight noise. .Oppositely arranged supply and exhaust valves of the puppet type are utilized, and means are provided,ioperable during the low pressure movement of the piston, but at a. high pressure for positively closing the exhaust valve to prevent escape of the low pressure gases of combustion.

In the accompanying drawings I have illustrated one complete example of the physical embodiment of my invention where-l in the valve operating' mechanism is adapted for use with the type of engine heretofore referred to, but it will b e understqod that the valve operating mechanism of my invention is applicable for use with other types of engine, the exempliication herein illust-rated showing the best form ofY adaptation l have so far devised'for the practical tion.

Figure l is a View showinofpartly in v,side

an internal Icombustion engine necessary' for View at line 22of Figure lof exhaust ,Y

valve Aand itsioperatingmechanism and connections..

'Fslire .e s an enlarged, transverse Seetional `view at'lin'e 3 8 `off Figure?. L

.For a clear` understanding oft'he'eons'truceen" and' epzerefien of erlesene@ parte 'ef the 4.internal kcombustion engine I' -have illus'- trated in Eigure l a singlefcylinder vengine having the usual crank :case: I and `ufanl;l shaft "2 supported in bearings '3, and the @e111 Shaft 4 Shown in dette@ klinee..ie/eupported inv journal bearings' suitable manner. y'Ihei'cam shaft -is properly timed with relation to the crank shaft and actuated therefrom' bythe large gear 6 e311.-V the shaft and the' pinion V7 Yon .the V,crank shaft for opening theinletv valve 8,"the it'ransfer valve/9 andbalance'valve 1Q', andthe vexhaust valve' 1,1, one of the camsbeingindicated at- 12 -(for the exlr-u'1st valvefin'Figure 2. i i

The engine or `motor illustrated comprises a differential cylindery having a lower 'hain-v .bei 13er Smau eiameterariuaitupper large;-

wo'rlring ehamber 14 in xcylinder oastng, in which the piston 15 reciprdcates withits enlarged head 16 inthe workingchamberor cylinderv of the engine. 'Ihe pStOQ isoperatively connected with `the vcranh shaft through the rod 17 and is actuated by high pressure beneath the headon the upward `working stroke,` and bya lower pressure charge tothe transfer conduit is eontrolled l 2LP` licei-ier ef the Rrieeiples et wreef ,eo y

`above the head o'nfthe downward'stroke.

through the port v2OV and valve chaIriberiQfl A between the valves 9.and 10, the valveQ actuated at predetermined .intervals from 'the cam shaft.

The charge'is exploded simultaneouslyby alvv action of a spark plug 22 in the supply conduit and a second spark lug 23 located at the lower end of the working cylinder and on the side of the piston opposite'to the supply conduit. The piston head controls the passage of exhaust gases from the upper end of the working cylinder through the exhaust port 24 to the exhaust chamber 25, and the exhaust valve 11 controls the exhaust of gases from the chamber 25 through the exhaust outlet 26, the chamber and outlet being located in a casting forming an extension of the cylinder castingV For regulating the pressure above the piston with relation to high speed and low speed of the engine, I utilizea pressure equalizing pipe 27 having a port 28 opening to the working cylinder above the piston head through a vertical passage 29 yin the cylinder head 29. This equalizingpipe is provided with a regulating-.valve 30 and is connected to the exhaust chamber 25Y for controlling movement of gases of combustion between the upper end of the working cylinder and the exhaust chamber. -The valve 30 is preferably open at low speed and closed orV partially closed at high speed of the engine, and inasmuch as the inertia ofthe reciprocating parts of the engine at llow speed is not so great as under high speed conditions, the valve is utilized at'low speed to vopen and relieve pressure from the upper end of the working cylinder to the exhaust connection of theengine.

The operation of the exhaust valve 11 is timed with relation to the operation of the intake and transfer and balance valves,

vthe exhaust valve being positively opened once at each revolution of the cam shaft through the action of the 'cam 12 and the valve operating mechanism as will now be described. The puppet valve 11 is fashioned with a depending stem 31 slidable or reciprocable in the exhaust extension of the cylinder castin'r and it co-acts with a tappet having a head 32 for engagement by the rotating'cam 12 of the cam shaft 4. The tappet head is fashioned with a central socket member 33 having` an interior thread in which the tappet-stem 34 is threaded, and the lock nut 35 is employed to hold the stem in adjusted position with relation to the socket member or head. The tappet-head is fashioned with a cylindrical bearinev cup 32 which is reciprocable in the hollow, fixed casting 36 having a bearing bushing 37 therein for the cup. normally forced downwardly and the tappet maintained in operative relation lto its cam by means of a spring 38 bearing on the tappet-head and interposed between the head and the closed upper end 39.of the casting. l

The interior of the casting 36 is lubri- The tappet stem and tappet arev cated from the crank case by way of oil ducts 40 arranged in an annular series around the center of the tappet and affording communication between the crank case and the interior ofthe casting. v

In Figure 2 the valve 11 is shown in open position being supported from the cam 12 through the tappet-stem and valvestem the adjoining ends being alined and the two stems being enclosed and guided within the end 39 of the casting. As the cam revolves the tappet is forced down by its spring 33 and the tappet head 32 continues in engagement with the `cam or cam shaft at all times. Normally the spring 41, which surrounds the valve stem andis interposed between the washer 42 fixed on the stem and the casting, holds the valve in open position. But during the downward movement of the piston on its low pressure stroke, the exhaust port 24 is exposed, and means are thus required to close the exhaust Valve during the low pressure Vexpansion action above the piston head. y

This closing of the exhaust valve against the tension of its spring 41 is accomplished by high pressure gas from the working cyl'- inder 14, and a high pressure pipe 43 having an' outlet port 44 from the cylinder is utilized to convey the gas under pressure to be used as a motive fluid. The upper end of the exhaust chamber 24 is closed by a plug 45 threaded into the exhaust extension of the cylinder casting, and the plug is provided with an inlet port 46 from the upper end of the motive fluid pipe 43. The plug is fashioned with a cylinder 47 opening at its lower end into the exhaust chamber, and a pressure actuated piston 48 is reciprocable in the cylinder, said piston having a short stem 49 bearing against the upper face of the exhaust valve.

The piston is lubricated through the annular groove 50 in the wall of the cylinder, and the plug 51 for an oil cup (not shown) supplies the lubricant to the groove through the duct 52 of the larger plug 45. ThusV when the fuel charge is exploded in the working cylinder a charge of expanded gas is passed through the pipe 43 to the cylinder 47, to act as a motive fluid, and by pressure in the cylinder 47 force the piston 48 downwardly with its stem against the exhaust valve. This movement of the piston closes the valve against the tension of the spring 41, and the entire assembly of the valve operating mechanism is thus brought together without lost motion or noise or shock, the cam rolling from under the tappet head 32 at the required instant. On the up stroke, the valve 11 closes immediately after firing, but not before the piston head 16 has closed the exhaust port 24 against escape of expanded gas at low pressure. Y

intake-valve 8 at predetermined intervals Gil through thevaction ofthe shaft l and cam operating mechanism for said valve. The fuel charge is admitted to the transfer chamber 18 and is drawn into the cylinder of the engine on theup stroke of the piston. On

its succeeding downl stroke this admitted charge of fuel is compressed, the intake valve 8 and transfer valve 9 being closed. The compressed fuel charge is now fired 'i causing the working or up stroke of the piston. Upon its next down stroke (with valve 8 closed and transfer valve 9 opened by its operating mechanism) the piston forces this low pressure, expanded gas through chamber 18 and pipe 19 to the .upper part of the cylinderl above its piston head for further expansion at low pressure te assist in moving the piston on its down stroke. vDuring the transfer of low pressure gas to the upper end of the cylinder` the exhaust valve 11 is closed by pressure from the lower end of the cylinder through pipe 43, which pressure acts upon piston 48 to close the exhaust valve. After the piston uncovers port 24 the exhaust valve is opened for outlet of the spent gas.

During the suction stroke of the piston the transfer valve 9 is closed and consequently the upward movement of the piston forces spent gas to the exhaust chamber through port 24 and also through pipe 27 and its valve 30 (if ope-n) to said chamber.

By compressed low pressure fluid in the upper lend of the cylinder above the port 24, the action of a dash pot is effected and this fluid assists in starting the piston on its down stroke.

The clearance space above the exhaust port 24 is of such capacity as to bring the compression of fluid therein to the required pressure in order'that it will overcome the inertia of the piston at the highest engine speed. By this utilization of the clearance space between the piston head and cylinderhead, transfer conduit 19, exhaust port 24 and exhaust chamber 25, equalizing pipe 27 and its port 28 (which parts are filled with compressed fluid) the whipping action of the piston is absorbed. When this clearance space is filled with compressed fluid more pressure is obtained from the high pressure gas as it is equalized throughout the cylinder, for the reason that the clearance space has been filled with motive fluid at a pressure suiiicient to overcome the inertia of the piston at the speed at which the engine is operating. This compression pressure is regulated by the valve 30 in the equalizing pipe 27. The higher the speed of the engine the greater the pressure required to vcushion it,and the lower fthe-.speed of the engine, a lesser pressure is required to cushion it.

The function of the equalizing pipe is tp convey the-released, excess, liuid from the chamber above the piston to the exhaust chamber v25 and thence to the atmosphere, on every `stroke of the piston except the working, down stroke. On this latter stroke the exhaust valve is closed and the fluid is thereby retained in the exhaust vchamber-25 whichspace is filled with the compressed fluid from above the piston through pipe 27. The quantity of fluid thus passing` through the Vpipe 27 is regulated by the valve 30.

It will be seen by reference to the drawings that the exhaust port 24 and chamber' 25 would not be filledwith the compressed Huid if the pipe 27 were not present, as the compression takes place between exhaust portl 24and the top of the cylinder The effect of the'operation and arrangement of the parts thus described is to produce conditions in a gas engine approaching as nearly as possible to similar conditions existing in a reciprocating steam engine.

W'hen the gases expand below -at-mosy pheric pressure in the cylinder, the spring L.t1 automatically lifts valve 11 from its seat to permit equalization of pressure through port 26 for the purpose of breaking a vacuum or partial vacuum existing in the engine cylinder. Thus under normal conditions the valve 1 1 is operated from the cam shaft, but should a vacuum or partial vacuum exist or be formed in the engine cylinder the valve is automatically opened by the spring al1. Under these automatically operating conditions the engine is enabled to deliver more power and at the same time economize in the consumption o-f fuel.

This automatic action is especially valuable in an aircraft engine in case the power fails and a vacuum or partial vacuum should result in the engine cylinder. Under such conditions the pistons in the engine will perform the functions of brakes to dangerouslv retard the revolution of the propeller. By the automatic opening of the valve this dangerous condition is overcome and consequently the aircraft is enabled to drift until power can again be applied, or a landing effected.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is 1. Tn an internal combustion engine the combination with a cylinder having an in-A ing the exhaust valve,I a fluid pressure actuated device for periodically holding said exhaust valve in its seat, means for conveying motive fluid from said cylinder to said pressure actuated device and means for automatically opening the exhaust valve to equalize pressure of gases expanded below atmospheric pressure in the engine.

2. The combination with a cylinder having an intake valve, an intake port, and an exhaust port adapted to be closed by the engine piston, of an exhaust chamber having a valve seat, an exhaust valve and its stem, a co-axial tappet and rotary cam for opening said exhaust valve, an auxiliary cylinder and its piston alined with the exhaust valve, means for supplying motive fluid to the auxiliary cylinder for closing the exhaust valve at predetermined intervals and means for automatically opening the exhaust valve to equalize pressure ot gases expanded below atmospheric pressure in the engine.

3. The combination with a cylinder having an intake valve and an intake port at its upper end, an exhaust chamber having a valve seat, and an exhaust port below the intake port adapted to be closed by the engine piston, of an exhaust valve and its stem, a co-axial tappet land rotary cam for positively opening the exhaust valve, an auxliary cylinder and its piston alined with the exhaust valve, means for supplying motive fluid to the auxiliary cylinder for closing the exhaust valve at predetermined intervals and resilient means for normally holding said exhaust valve open when released. v

4. In combination with a valve and its stern and a hollow casing, of a tappet within said casing and an actuating cam therefor, resilient, Vmeans for holding the tappet in operative relation to the cam, resilient means tor opening the valve when said tappet` is inoperative, and pressure actuated means above the valve for closing the valve at predetermined intervals. y

5. n combina-tion with a valve and its stem and a hollow casing, of a tappet within the casing and an actuating cam therefor, a spring within the casing` Jfor holding the tappet in operative position relative to the cam, a spring between said casing and the valve for opening the valve when said tappet is inoperative, and pressure actuated means above the valve for positively closing' the valve at predetermined intervals.

In testimony whereof I have allixed my signature.

EITWARD W. MER-EDITH. 

